If you thought pertussis was history, think again. Since 1980 the number of cases in the U.S. has risen to more than 3 million a year. Pertussis, also known as whooping cough, is the only vaccine-preventable disease that is on the rise.

The Pertussis vaccine became available in 1940 and there was a steady decline of this deadly childhood disease in the U.S. until 1980. More cases are now being reported among adults and adolescents who experience a milder, but just as stubborn form of the disease as infants. Since pertussis initially resembles other common colds, the disease is probably under reported.

Babies under the age of 1 get the infection from those who are closest to them. Family members, friends and caregivers are usually the source. We have only recognized in recent years the role of adults around an infant to be a potentially dangerous reservoir of the disease. Adults are susceptible to pertussis because the vaccine they received as children wanes over five to 10 years. If one member of a household has whooping cough, there’s a 90 to 100 percent chance that other susceptible household members will also catch it.

The vaccine is administered at 2, 4 and 6 months of age. A fourth dose is administered between 12 and 18 months, and a fifth after age 4. Teens need another booster shot between 11 and 18. All adults should have a single adult booster of Tdap (tetanus, diphtheria, and acellular pertussis) vaccine.

Even when a baby is vaccinated, they may not be fully protected until they have received at least three doses of the infant pertussis vaccine. In order to create a “cocoon of safety” around an infant, those in close contact with the baby should receive a single dose of Tdap.

Whooping cough is spread easily through mucus droplets, broadcast by profound coughing and sneezing. It can take three weeks or more to develop symptoms after exposure to the infection. Individuals can give whooping cough to others until they’ve been treated with antibiotics for five days, or until coughing for 21 days.

The swelling and inflammation to airways is actually caused by toxins secreted by the bacteria. After 21 days of the infection the bacteria will die off, but has already released damaging toxins.

Early recognition and treatment is important to minimizing the effects and preventing spread of the acute infection to others. Pertussis causes spells of coughing that makes it hard for a child to eat, drink, or breathe. The cough is often followed by a “whooping” sound as the person gasps for air, which is how the condition got its name. Some historians referred to the disease as the “100-day cough.”

Serious side effects from the coughing fits are common in children. The choking and gasping can be fatal in children under the age of 1. The disease is most serious in infants, especially those too young to get the vaccine or not fully protected. Babies with whooping cough are often hospitalized. With older kids and adults, the disease is milder and can cause several weeks of exhausting coughs. Although rarely fatal in adults and older children, time lost from school and work is substantial.

Early detection is important in limiting the spread of whooping cough. Appropriate antibiotic therapy for the person suffering from the condition and their close contacts needs to be started as soon as possible. Late recognition and treatment fails to change the course of the disease. Many weeks of coughing by the affected individual will continue even if the spread is limited.

Testing specimens from a nasal swab can be helpful in identifying pertussis only in the first couple weeks. Many patients don’t seek medical evaluation until later and the results of testing also causes further delay. Precise recognition can be difficult. Treatment is often started in the context of clinical symptoms and known outbreak in the community.

This punctuates the importance of prevention and a proactive approach to immunizations of both children and adults in the community. The best way to help protect babies against pertussis is to get infant vaccinations in a timely fashion. Adolescents and adults should have a single dose of Tdap booster.